Arginine residues ribonuclease

The structure-activity relationships of bovine pancreatic ribonuclease I have been examined. About 90% of the enzymic activity was lost on modification of two thirds of the L-arginine residues with cyclohexanedione. 

Enzymes which catalyze the hydrolysis of the unit linkage of sequential residues of oligomers or polymers determine their substrate specificity by recognizing the particular unit residue in the sequential chain as well as the direction of the chain. For example, ribonuclease cleaves the 3 -phosphate of a pyrimidine nucleotide residue but not the 5 -phosphate, and trypsin hydrolyzes peptide bonds which involve the arginine or lysine residue at the carbonyl end but not at the amino end. This is also the case for the hydrolysis of a variety of synthetic substrates and quasi-substrates (Sect. 4.1). Synthetic trypsin substrates are ester or amide derivatives in which the site-specific group (positive charge) is contained in their carbonyl portion. 

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